/**
 * Created with IntelliJ IDEA.
 * Description:
 * User:26554
 * Date:2024-11-04
 * Time:14:31
 */
public class tt {
    public static void main(String[] args) {
        double a = 0.0;
        double b = 0.0;
        double ret = 0.0;
        for (int i =1 ; i < 100; i+=2) {
            a+=1.0/i;
        }
        for (int i = 2; i <= 100; i+=2) {
            b+=1.0/i;
        }
        System.out.print(a-b);
    }
}
